1. Field of the Invention
The present invention relates to a wafer cleaning apparatus, and more particularly, to an improved wafer cleaning apparatus which is capable of upgrading wafer cleaning effectiveness by spraying a cleaning solution in varying directions towards a wafer.
2. Description of the Related Art
In semiconductor fabricating processes, the wafer cleaning procedure is basically directed to preventing the surface of a wafer from being contaminated by contaminants such as organic substances, dust or the like, because scrupulously clean wafers are critical for obtaining high yields in very large scale integration (VLSI) fabrication.
Generally, in the wafer cleaning procedure, a wafer is immersed in a sulfuric acid (H.sub.2 SO.sub.4)-hydrogen peroxide (H.sub.2 O.sub.2) mixture to remove organic contaminants or ionic contaminants adhered thereto, and then is rinsed in deionized water to repel acid or alkali.
In order to upgrade the effectiveness of the rinsing procedure using deionized water, a sequence of step are carried out, including for example, a pre-rinsing step during which deionized water is filled to capacity in a cleaning bath then quickly dumped, a dump rinsing step during which deionized water and nitride gas N.sub.2 are cooperatively used to remove dust, or the like, from the surface of the wafer, and a post-rinsing step during which the wafer is placed in flowing water.
A quick dump rinsing (QDR) step can be utilized to quickly and cleanly rinse contaminants such as a chemical or the like existing on the surface of a wafer. Referring to FIG. 1, there is illustrated a conventional wafer cleaning apparatus including a QDR bath. The conventional wafer cleaning apparatus 10 includes a cleaning bath 2 in which a wafer (not shown) is received to be cleaned by deionized water and nitride gas N.sub.2, a plurality of spaced-apart injection nozzles 4 vertically arranged at both side walls of the cleaning bath 2, and a plurality of spaced-apart holes 6 formed at the bottom surface of the cleaning bath 2 to allow the deionized water and the nitride gas N.sub.2 to be introduced and dumped therethrough.
In the wafer cleaning apparatus 10 constructed as mentioned above, after the wafer having contaminants adhered thereon is placed in the cleaning bath 2, the deionized water and the nitride gas N.sub.2 are supplied through the plurality of holes 6 into the cleaning bath 2 to first remove contaminants from the wafer. In the course of draining the deionized water and the nitride gas N.sub.2, when the wafer is exposed to the outside, more deionized water is sprayed onto the wafer through the plurality of injection nozzles 4 at a high pressure to clean the wafer again. These cleaning operations using the deionized water and the nitride gas N.sub.2 are implemented for three to five cycles.
However, the conventional wafer cleaning apparatus has a drawback in that since the plurality of injection nozzles 4 are fixed in one direction, it is possible that a portion of the wafer may not be wetted by the sprayed water, resulting in an insufficient cleaning procedure. If the pressure of the sprayed water is reduced, the effectiveness of wafer cleaning procedure is further deteriorated. Moreover, since the same cleaning cycles are repeatedly used, additional time is needed to complete the cleaning procedure such that productivity is lowered remarkably.